Because 'imagejpeg', 'imagegif' and 'imagepng' has their own parameters especially quality value, following function is required if you want to customize quality value.
private function write_image($new_img, $new_file_path, $write_image){
if($write_image == 'imagepng'){
return $write_image($new_img, $new_file_path, 0);
}else if($write_image == 'imagegif'){
return $write_image($new_img, $new_file_path);
}else{
return $write_image($new_img, $new_file_path, 100);
}
}
http://php.net/manual/en/function.imagepng.php